Underground tanks are used to collect and store rainwater for later use such as for watering gardens, flushing toilets, washing machines and cars, agriculture, and for drinking, thereby conserving water and providing many economic and environmental benefits.
Underground tanks can be formed from plastic perforated tank modules, which are butted or stacked together to form the required tank size, wrapped in geotextile and surrounded in good draining medium such as sand. The geotextile material allows water to pass therethrough but prevents any sand from passing. Thus, water flows into the tank via a connecting pipe and percolates into the surrounding strata through the geotextile-covered perforated modules of the tank. Similarly, water percolating through the soil above the tank enters the tank through the geotextile-covered top perforated module of the tank.
Some existing underground tank modules use a large amount of plastic material and contain a small void volume such that water flow through the modules is restricted. Others provide a large void volume for better flow of water through the modules, but have a considerably weak structure.
Accordingly, a need exists for an improved module for underground tanks which would provide adequate void space and water flow through as well as a strong geotextile-supporting skeleton.